This invention relates to a circuit mounting arrangement and a housing assembly for a pair of complementary circuits such as a sensing element and switching circuit controlled thereby of a metal proximity sensing limit switch.
Electrically powered machinery is often controlled by limit switches which control the application of power to the machinary in accordance with the position of a moving part thereof. In numerous applications, food processing machinery for instance, the machinery is subjected to frequent steam or water cleaning or the like. In other applications, the machinery, and thus the limit switches associated therewith, are subjected to other fluids harmful to the limit switches and the wiring connected therewith. Accordingly, safe and trouble-free operation frequently requires that the power-carrying wiring connected between the limit switch and the source of power and the load be contained within wiring conduit and the limit switch circuitry itself be contained within a protective housing joined with the conduit.
Despite the existence of electronic limit switches which are free of numerous disadvantages such as contact corrosion and mechanical wear of mechanical limit switches, mechanical limit switches are still widely employed. An important factor discouraging owners of machinery from replacing mechanical limit switches with electronic limit switches is the cost of doing so.
The cost of replacement includes the cost of labor for doing the replacement work as well as the purchase price of the electronic limit switch. Factors contributing to the cost of a limit switch assembly, which includes a housing in addition to the controlled switching circuit and sensing element, are the cost of manufacturing the housing, the labor cost in assembling the circuit with the housing, the cost of mounting elements necessary to secure the circuit to the housing and to make electrical connection with external circuitry and the factors which prevent obtainment of economies of scale.
The designs of known electronic limit switch assemblies have prevented the minimization of both the cost of the switch assemblies themselves and the cost of labor necessary for replacement.